The 29-year-old actress and writer has endometriosis, a female reproduction health disorder. It occurs when the tissue lining the uterus strays outside the womb and grows in places it is not supposed to. Aside from causing severe pain, it may cause infertility.

"As many of you know I have endometriosis, a chronic condition that affects approximately 1 in 10 women's reproductive health," Dunham wrote on Instagram as she shared the news.